Working with BIG numbers or LOTS of decimal places

[killo]

This code contains quite a few mathematical functions and is capable of handling very large numbers or numbers with lots of decimal places. the limit to how big a number they can handle is not 1.79769313486232E+308 which is the normal double limit, but 1.79769313486232E+308 DIGITS LONG!
functions included are: add, subtract, divide, multiply, square root, mod and power.
they work by using long division, long addition etc
they cannot handle negative numbers and the power function ( y^x ) only supports x being a whole number up to the size of double precision, but y can have decimals and be very large like the rest.
it also needs some work as i know they can be alot faster, any suggestions to make them faster will be greatly appreciated.
here they are, this must be put in a module:
UPDATES:
indented
improved code with si's suggestions
attatched a sample project which uses this module to calculate pi (end of second post)
improved again

'Long math functions by karl baker
'you are free to use these in your own projects as long as credit is given

Public Function divide(tnum1 As String, tnum2 As String, tplaces As String) As String

Dim result As String
Dim times As Long
Dim val3 As String
Dim loopcount As Long
Dim last As Boolean
Dim num1 As String
Dim num2 As String
Dim places As String
places = tplaces
num1 = tnum1
num2 = tnum2
last = False
'start the loop

Do
    'loopcount keeps track of how many dp we have calculated
    loopcount = loopcount + 1
    result = 0
    times = 0
    'see how many times num1 goes into num2
    Do Until morethan(result, num1)
        result = add(result, num2)
        times = times + 1
        
    Loop
    result = subtract(result, num2)
    times = times - 1
    'if num1 goes into num2 exactly then this is the last calculation we need to do
    If result = num1 Then last = True
    
    If loopcount <> places And last = False Then
        val3 = subtract(num1, result)
        'multiply num1 by 10 to use in the next loop round for calculating the next digit
        num1 = multiply(val3, 10)
    End If
    
    If loopcount = 1 And last = False Then
        divide = times & "."
    Else
        divide = divide & times
    End If
DoEvents
Loop Until loopcount = places Or last = True
    
    
    
 If InStr(divide, ".") > 0 Then
  Do While Right(divide, 1) = "0"
    divide = Left(divide, Len(divide) - 1)
  Loop
End If
    



End Function

Public Function sqrt(tnum1 As String) As String
Dim num1 As String
num1 = tnum1
Dim tempnum1 As String
Dim lastnum As String
Dim multiply1 As String
tempnum1 = 2
lastnum = 1

Do
    'square tempnum
    multiply1 = multiply(tempnum1, tempnum1)
    'if tempnum^2 is bigger than num1 then we know we have found the square root
    If morethan(multiply1, num1) Then Exit Do
    lastnum = tempnum1
    'add the appropriate number to tempnum
    If morethan(subtract(num1, multiply1), 1000000000000#) Then
        tempnum1 = add(tempnum1, 1000000)
    ElseIf morethan(subtract(num1, multiply1), 10000000000#) Then
        tempnum1 = add(tempnum1, 100000)
    ElseIf morethan(subtract(num1, multiply1), 100000000) Then
        tempnum1 = add(tempnum1, 10000)
    ElseIf morethan(subtract(num1, multiply1), 1000000) Then
        tempnum1 = add(tempnum1, 1000)
    ElseIf morethan(subtract(num1, multiply1), 10000) Then
        tempnum1 = add(tempnum1, 100)
    ElseIf morethan(subtract(num1, multiply1), 100) Then
        tempnum1 = add(tempnum1, 10)
    ElseIf morethan(subtract(num1, multiply1), 50) Then
        tempnum1 = add(tempnum1, 5)
    ElseIf morethan(subtract(num1, multiply1), 10) Then
        tempnum1 = add(tempnum1, 3)
    Else
        tempnum1 = add(tempnum1, 1)
    End If
DoEvents
Loop
sqrt = lastnum
End Function

Public Function Lmod(tnum1 As String, tnum2 As String) As String
Dim result As String
Dim num1 As String
Dim num2 As String
num1 = tnum1
num2 = tnum2
result = 0

Do Until morethan(result, num1)
    result = add(result, num2)
DoEvents
Loop

'subtract to get the remainder we're after
Lmod = subtract(result, num1)
If Lmod = tnum2 Then Lmod = 0


End Function


Public Function add(tnum1 As String, tnum2 As String) As String
Dim num1 As String
Dim num2 As String
num1 = tnum1
num2 = tnum2
Dim i As Long
Dim length As Long
Dim temp As Byte
Dim carry As Byte

checkdec:
'check whether the numbers contain a decimal place
If InStr(num1, ".") > 0 And InStr(num2, ".") > 0 Then
    'if they do then format them so that the decimal place is in the same pasition for both of them
    If (Len(num1) - InStr(num1, ".")) < (Len(num2) - InStr(num2, ".")) Then
        Do
            num1 = num1 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    ElseIf (Len(num1) - InStr(num1, ".")) > (Len(num2) - InStr(num2, ".")) Then
        Do
            num2 = num2 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    End If
    
ElseIf InStr(num1, ".") > 0 And InStr(num2, ".") = 0 Then
    num2 = num2 & "."
    GoTo checkdec
ElseIf InStr(num1, ".") = 0 And InStr(num2, ".") > 0 Then
    num1 = num1 & "."
    GoTo checkdec
End If

If Len(num1) > Len(num2) Then
    length = Len(num1)
    num2 = String$(length - Len(num2), "0") & num2

ElseIf Len(num2) > Len(num1) Then
    length = Len(num2)
    num1 = String$(length - Len(num1), "0") & num1
Else
    length = Len(num1)
End If

carry = 0
'start adding the numbers together
For i = 1 To length
    If Mid(num1, (length - i + 1), 1) = "." Then
        add = "." & add
    Else
        temp = Val(Mid(num1, (length - i + 1), 1)) + Val(Mid(num2, (length - i + 1), 1)) + carry
        If temp < 10 Then
            add = temp & add
            carry = 0
        Else
            add = Right(temp, 1) & add
            carry = Left(temp, 1)
        End If
    End If

Next i

If carry > 0 Then add = carry & add


    Do While Left(add, 1) = "0"
   add = Right(add, Len(add) - 1)
    Loop

If Left(add, 1) = "." Then add = "0" & add



End Function

Public Function morethan(tnum1 As String, tnum2 As String) As Boolean
Dim i As Long
Dim length As Long
Dim temp As Byte
Dim carry As Byte
Dim num1 As String
Dim num2 As String
num1 = tnum1
num2 = tnum2

checkdec:
'format just like in add
If InStr(num1, ".") > 0 And InStr(num2, ".") > 0 Then
    If (Len(num1) - InStr(num1, ".")) < (Len(num2) - InStr(num2, ".")) Then
        Do
            num1 = num1 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    ElseIf (Len(num1) - InStr(num1, ".")) > (Len(num2) - InStr(num2, ".")) Then
        Do
            num2 = num2 & "0"
        Loop Until (Len(num1) - InStr(num1, ".")) = (Len(num2) - InStr(num2, "."))
    End If
ElseIf InStr(num1, ".") > 0 And InStr(num2, ".") = 0 Then
    num2 = num2 & "."
    GoTo checkdec
ElseIf InStr(num1, ".") = 0 And InStr(num2, ".") > 0 Then
    num1 = num1 & "."
    GoTo checkdec
End If

If Len(num1) > Len(num2) Then
    length = Len(num1)
    num2 = String$(length - Len(num2), "0") & num2

ElseIf Len(num2) > Len(num1) Then
    length = Len(num2)
    num1 = String$(length - Len(num1), "0") & num1
Else
    length = Len(num1)
End If

morethan = False

'check if it is more than the other
For i = 1 To length
    If Mid(num1, i, 1) <> "." Then
    Select Case Val(Mid(num1, i, 1))
        Case Is > Val(Mid(num2, i, 1))
            morethan = True
            Exit Function
        Case Is < Val(Mid(num2, i, 1))
            morethan = False
            Exit Function
        End Select
    End If

Next i

End Function

continued in next post